It is well known in the prior art that high speed switching circuits need to be properly terminated in order to ensure proper performance. By terminating such circuits, signal reflections which would create voltage standing waves and result in waveform distortion may be minimized. The suppression of voltage standing waves has been a long standing problem typically experienced in radio frequency circuits. However, as modem computer circuits feature increased operating speeds, proper termination of these computer circuits is now also critical.
The most difficult circuitry to terminate is that which is interconnected by a cable assembly. This is especially true where a number of circuits may be interconnected by a single cable. Such an application is found in the Small Computer System Interface (SCSI) bus system. The SCSI bus standard sets forth a multiconductor bus structure which requires termination at both the signal source and signal destination. In addition to providing the desired impedance matching, the terminator in a SCSI bus assists in establishing the required voltage at the time of signal negation and establishing the required current lead at the time of signal assertion. Several attempts have been made to terminate such circuitry in the prior art.
For example, U.S. Pat. No. 4,610,493 to Masek ('493 patent) illustrates a terminator for multiconductor ribbon cable. The terminator of the '493 patent includes a base, a terminator circuit and a cover. The base and cover snap together to depress insulation displacement contacts from the terminator circuit into the ribbon cable. This approach requires a full mechanical assembly which is separate from a connector which interconnects the circuits. Further, as the '493 patent is directed to a separate terminator assembly, the circuits are necessarily terminated at a point physically removed from the actual interconnection. This type of terminator assembly is illustrated in FIG. 1. A cable assembly 1 includes plural connectors 2 terminated to cable 3 in longitudinal spaced-apart succession. A terminator assembly 4 is shown terminating an end extent of a cable extension 6. The separation introduced by the cable extension 6, however small, allows a voltage standing wave to form.
A further example of a terminator device known in the prior art is illustrated in U.S. Pat. No. 4,932,873 to La Shier ('873 patent). The '873 patent describes a terminator assembly suitable for use in multiconductor ribbon cable. The '873 patent discloses a terminator assembly formed using a standard dual in-line package (DIP) carrier having insulation displacement contacts as part of the assembly. The DIP carrier forms a base to support terminator circuit components. Top and bottom covers are included which snap the assembly together forcing the insulation displacement contacts of the terminator assembly into the cable to be terminated. The '873 patent is formed as an assembly which is separate from any connector on the cable. Therefore, this device has similar disadvantages to that of the '493 patent.
U.S. Pat. 4,954,089 to Jensen et al. ('089 patent) discloses a terminator which is formed as an interconnect device having both male and female connections. This device is suitable for terminating cables which include a separate connector assembly which mates with the terminator. While the '089 device allows connections to be terminated in close proximity to the point of interconnection, the '089 device requires a separate mechanical structure which has the equivalent complexity of two connectors. As the '089 device is a separate assembly from the connector itself, it necessarily adds additional cost and size to the terminated cable assembly.
Another terminator design is disclosed in U.S. Pat. No. 5,472,348 to Daly et al. ('348 patent). The device in the '348 patent is a plugable male terminator assembly which includes male connector pins, a terminator circuit connected to these pins and a housing enclosing the pins and circuitry. The terminator of the '348 patent is designed to mate with the female connector structure which would be mounted on a multiconductor cable to be terminated. The device in the '348 patent has the disadvantages of the '089 patent in that it requires a full assembly which is separate from the cable connector itself. The '348 patent also shares the disadvantages of the '493 and '873 patents, in that this device will typically be mounted a distance away from the circuitry which is to be terminated.